ON THE FUNCTIONS OF THE CEREBRAL CORTEX. 
41 
" Tested on tlie tenth day after the operation, there is no reaction produced on 
pricking any part of the right arm, and only a very slow reaction on applying a 
similar stimulus to the right side of the trunk and to the right ear. The leg reacts 
more readily, but is distinctly less sensitive than the left leg." 
After this time the condition as regards sensibility began slowly to improve, especially 
in parts. " Reaction is now obtained on stimulating the right hand and arm below the 
elbow, but none from the upper arm, and very little from the upper part of the trunk 
down to the level of the iliac crest. The right ear is still quite insensitive, but the 
side of the face is sensitive. The right foot is rather more sensitive than before, and 
indeed the whole lower limb reacts, although more slowly and less markedly than on 
the left side, both to tactile and painful impressions." 
Three months after the second operation the whole of the right side still showed a 
great diminution of sensibility as compared with the left. The difference was least 
marked in the arm at and below the elbow. The animal was then killed and the 
brain examined. 
It appears that the lesion involves the greater part of the gyrus fornicatus and the 
anterior portion of the quadrate lobule, but for a small extent, about 5 mm. in length, 
near the anterior end of the corpus callosum the convolution is almost intact. The 
gyrus marginalis is injured at two places, viz., to a small extent posteriorly, and also 
anteriorly in the prefrontal region. Close to the latter lesion there is a small patch 
of softening on the external surface. * 
The mesial surface of the left hemisphere is shown in fig. 37a (Plate 6), and four 
sections through the same hemisphere in figs. 37b, c, d, and e. The sections are 
taken at about the situation of the lines which are lettered correspondingly in 
fig. 37a. 
38.t 
Lesion. — The posterior part of the left hippocampal gyrus was scooped away, the 
occipital lobe being raised from behind and the scoop introduced beneath it. The 
result of this modus oj^erandi, as shown on post-mortem examination, was to cause 
extensive softening of the occipital lobe. Whether from this destructive process going 
on in the brain, or from some other unknown cause, the animal did not survive the 
operation more than seven days. During the whole of this interval there was 
considerable diminution of sensibility upon the right side as compared with the left, 
without any sign of motor paralysis. 
The superficial extent of the lesion is shown in fig. 38a, Plate 6, and the deep 
extent in the sections in figs. 38b, c, d, and e. 
* There was no perceptible paresis produced by tbe operation in this Monkey. The right band was 
used much less than the left, but many Monkeys are left-handed, and we had not previously determined 
whether this was such an one. Even had it not been so, the diminished use of the right hand might well 
have been produced by the loss of tactile sensibility of that limb. 
t This animal was exhibited to the Physiological Society, 
MDCCCLXXXVIII. — B. G 
